[0001] This invention relates to a process for preparing methyl acetate by reacting dimethyl
ether with carbon monoxide in the presence of a zeolite catalyst.
[0002] Methyl acetate is used industrially in petrochemical processes, particularly as a
feed for the production of acetic acid and/or acetic anhydride.
[0003] The commercial production of acetic acid is operated as a homogeneous liquid-phase
process in which the carbonylation reaction is catalysed by a Group VIII noble metal
such as rhodium or iridium and an alkyl iodide such as methyl iodide. The main drawbacks
of this process are the use of iodide which can lead to corrosion problems and the
difficulties associated with separation of the products and catalyst components from
a single phase. Both of these drawbacks could be overcome if a heterogeneous gas phase
process using an iodide free solid catalyst could be developed.
[0004] EP-A-0 596 632 describes a vapour phase process for the carbonylation of methanol to produce acetic
acid in the presence of a modified mordenite catalyst at high temperatures and pressures.
[0005] WO 01/07393 describes a process for the catalytic conversion of a feedstock comprising carbon
monoxide and hydrogen to produce at least one of an alcohol, ether and mixtures thereof
and reacting carbon monoxide with the at least one of an alcohol, ether and mixtures
thereof in the presence of a catalyst selected from solid super acids, heteropolyacids,
clays, zeolites and molecular sieves, in the absence of a halide promoter, under conditions
of temperature and pressure sufficient to produce at least one of an ester, acid,
acid anhydride and mixtures thereof. However, the use of zeolites to catalyse the
carbonylation reaction is not exemplified.
[0006] WO 2005/105720 describes a process for production of a carboxylic acid and/or an ester or anhydride
thereof by carbonylating an aliphatic alcohol or reactive derivative thereof with
carbon monoxide in the substantial absence of halogens in the presence of a modified
mordenite catalyst at a temperature in the range 250 - 600 °C and a pressure in the
range 10 to 200 bar. The use of dimethyl ether as a feedstock is not exemplified.
[0007] WO 2006/121778 describes a process for the production of a lower alkyl ester of a lower aliphatic
carboxylic acid by carbonylating under substantially anhydrous conditions a lower
alkyl ether with carbon monoxide in the presence of a mordenite or ferrierite catalyst.
According to this patent application, the carbonylation process is run at temperatures
at or below 250 °C, and preferably from about 150 to about 180 °C to minimise by-product
formation.
[0008] In view of the above-mentioned prior art, there remains the need for a heterogeneous
gas phase process for the production of methyl acetate from dimethyl ether under substantially
anhydrous conditions using a zeolite catalyst which is superior to the other processes
using carbonylatable reactants as a feed.
[0009] It has now been found that if the carbonylation process is carried out at a temperature
in the range of greater than 250 °C to 350 °C and at a pressure in the range of 30
to 80 barg then improved productivities and/or selectivities may be achieved.
[0010] Accordingly, the present invention provides a process for the production of methyl
acetate which process comprises the carbonylation of a dimethyl ether feed with carbon
monoxide under substantially anhydrous conditions such that water is present in the
dimethyl ether feed in an amount of 2.5wt% or less, in the presence of a zeolite catalyst
effective for said carbonylation, wherein said carbonylation is carried out at a temperature
in the range of greater than 250 °C to 350 °C and at a pressure in the range of 30
to 80 barg.
[0011] The present invention solves the problem defined above by operating the process at
high temperature and high pressure to give good selectivities and/or productivities
to methyl acetate product. The finding that this can be achieved at high temperatures
and pressures is surprising because from the work described in
WO 2006/121778 mentioned above, it would be expected that the effect of increasing the reaction
temperature of a zeolite-catalysed carbonylation of dimethyl ether would be merely
to significantly reduce the methyl acetate formation rate and selectivity thereto.
Furthermore, methanol carbonylation in the presence of a zeolite catalyst generally
requires a reaction temperature of greater than 250 °C thus it would be expected that
the productivities and/or selectivities achieved by the carbonylation of dimethyl
ether under the same reaction conditions as the carbonylation of methanol would be
inferior.
[0012] The dimethyl ether used as the feed in the process of the present invention may be
substantially pure dimethyl ether. In commercial practice, dimethyl ether is produced
by the catalytic conversion of synthesis gas (mixtures of hydrogen and carbon monoxide)
over methanol synthesis and methanol dehydration catalysts. This catalytic conversion
results in a product which is predominantly dimethyl ether but it may also contain
some methanol. In the process of the present invention the dimethyl ether feed may
comprise small amounts of methanol provided that the amount of methanol present in
the feed is not so great as to inhibit the carbonylation of dimethyl ether to methyl
acetate product. It has been found that less than 5 wt%, such as less than 1 wt% of
methanol in the dimethyl ether feed may be tolerated.
[0013] Suitably, dimethyl ether is present in the feed at a concentration in the range of
0.1 to 20 mol%, for example 1 mol% to 20 mol%, such as 1.5 to 10 mol%, for example,
1.5 mol% to 5 mol%, based on the total feed (including recycles).
[0014] The carbon monoxide may be substantially pure carbon monoxide, for example, carbon
monoxide typically provided by suppliers of industrial gases, or it may contain impurities
that do not interfere with the conversion of the dimethyl ether to methyl acetate,
such as nitrogen, helium, argon, methane and/or carbon dioxide.
[0015] The carbon monoxide feed may contain hydrogen. Mixtures of hydrogen and carbon monoxide
are commercially produced by the steam reforming of hydrocarbons and by the partial
oxidation of hydrocarbons. Such mixtures are commonly referred to as synthesis gas.
Synthesis gas comprises mainly carbon monoxide and hydrogen but may also contain smaller
quantities of carbon dioxide.
[0016] Suitably, the molar ratio of carbon monoxide : hydrogen may be in the range 1 : 3
to 15 : 1, such as 1 : 1 to 10 : 1, for example, 1 : 1 to 4 : 1.
[0017] The molar ratio of carbon monoxide to dimethyl ether is suitably in the range 1 :
1 to 99 : 1, such as 2 : 1 to 60 : 1.
[0018] The zeolite catalyst may be any zeolite which is effective to catalyse the carbonylation
of dimethyl ether with carbon monoxide to produce methyl acetate.
[0019] Zeolites are available from commercial sources, generally in the Na, NH
4 form or H- form of the zeolite. The NH
4 form can be converted to the acid (H-form) by known techniques, such as calcination
at high temperature. The Na form can be converted to the acid (H-form) by converting
first to an NH
4 form by ion exchange with ammonium salts such as ammonium nitrate. Alternatively,
zeolites may be synthesised using known techniques.
[0020] Zeolites comprise a system of channels which may be interconnected with other channel
systems or cavities such as side-pockets or cages. The ring structures are generally
12-member rings, 10-member rings or 8 member rings. A zeolite may possess rings of
different sizes. The zeolites for use in the present invention preferably contain
at least one channel which is defined by an 8-member ring. Most preferably, the 8-member
ring channel is interconnected with at least one channel defined by a ring with 10
and/or 12 members. The window size of the channel systems should be such that the
reactant dimethyl ether and carbon monoxide molecules can diffuse freely in and out
of the zeolite framework. Suitably, the window size of an 8-member ring channel may
be at least 2.5 x 3.6 Angstroms.
The Atlas of Zeolite Framework Types (C. Baerlocher, W. M. Meier, D. H. Olson, 5th
ed. Elsevier, Amsterdam, 2001) in conjunction with the web-based version
(http://www.iza-structure.org/databases/) is a compendium of topological and structural details about zeolite frameworks, including
the types of ring structures present in a zeolite and the dimensions of the channels
defined by each ring type. Examples of zeolites suitable for use in the present invention
include zeolites of framework type MOR, for example mordenite, FER, such as ferrierite,
OFF, for example, offretite and GME, for example gmelinite.
[0021] For the process of the present invention it is preferred that the zeolite has a silica
to alumina ratio of at least 5 but preferably less than or equal to 100, such as in
the range 7 to 40, for example 10 to 30. Where the aluminium atoms have been replaced
by framework modifier elements such as gallium, it is preferred that the ratio of
silica: X
2O
3 where X is a trivalent element, such as aluminium, gallium, iron and/or boron, is
at least 5 and preferably less than or equal to 100, such as in the range 7 to 40,
for example 10 to 30.
[0022] In one embodiment of the present invention the zeolite catalyst is a mordenite zeolite.
The mordenite may be employed in the acid form (H-mordenite) or it may be optionally
ion-exchanged or otherwise loaded with one or more metals such as copper, silver,
nickel, iridium, rhodium, platinum, palladium or cobalt.
[0023] The metal loading on the mordenite zeolite may be expressed in terms of the fractional
loading of the metal as gram atoms of metal per gram atom of aluminium in the mordenite.
The metal loading can also be expressed as a mole percentage loading relative to aluminium
in the mordenite through the relationship :
Thus, for example, a loading of 0.55 gram atoms of copper per aluminium in the mordenite
equates to a 55 mol% loading of copper relative to aluminium in the mordenite.
[0024] Suitably, the metal loading may be in the range of 1 to 200 mol% relative to aluminium,
such as 50 to 120 mol%, for example, 50 to 110 mol% or 55 to 120 mol%, such as 55
to 110 mol%.
[0025] The mordenite framework, may in addition to the silicon and aluminium atoms, contain
additional trivalent elements, such as boron, gallium and/or iron.
[0026] Where the mordenite contains at least one or more trivalent framework, the metal
loading in the mordenite can be expressed in terms of the fractional loading of the
metal as gram atoms of metal per gram atom of total trivalent elements in the mordenite.
The metal loading can also be expressed as a mole percentage loading relative to total
trivalent elements in the mordenite through the relationship :
[0027] Because the carbonylation reaction is to be conducted substantially in the absence
of water, it is preferred that the zeolite catalyst is dried prior to use. The zeolite
may be dried, for example by heating to a temperature of 400 to 500 °C.
[0028] It is preferred that the zeolite catalyst is activated immediately before use by
heating the zeolite at elevated temperature for at least one hour under flowing nitrogen,
carbon monoxide, hydrogen or mixtures thereof.
[0029] The process is carried out under substantially anhydrous conditions, i.e in the substantial
absence of water. The carbonylation of dimethyl ether to methyl acetate does not generate
water in-situ. Water has been found to inhibit the carbonylation of dimethyl ether
to form methyl acetate. Thus, in the process of the present invention, water is kept
as low as is feasible. To accomplish this, the dimethyl ether and carbon monoxide
reactants (and catalyst) are preferably dried prior to introduction into the process.
However, small amounts of water may be tolerated without adversely affecting the formation
of methyl acetate. In the process of the present invention, less than 2.5 wt% water,
for example, less than 0.5 wt% water may be present in the dimethyl ether feed.
[0030] The process of the present invention is carried out at a temperature in the range
of greater than 250 °C to 350 °C and at a pressure in the range of 30 barg to 80 barg.
Suitably, the temperature may be in the range 275 to 350 °C, for example, 300 to 350
°C or 275 to 325 °C.
[0031] Suitably, the process may be carried out at a temperature in the range 275 to 350
°C, such as 300 to 350 °C and at a pressure of 30 barg to 80 barg.
[0032] The Gas Hourly Space Velocity (GHSV) is suitably in the range 500 to 40,000 h
-1, for example, 1000 to 20,000 h
-1, such as 2000 to 20,000 h
-1.
[0033] The process of the present invention is suitably carried out by passing dimethyl
ether vapour and carbon monoxide gas through a fixed or fluidised bed of the zeolite
catalyst maintained at the required temperature and pressure.
[0034] Preferably, the process of the present invention is carried out substantially in
the absence of halides, such as iodide. By the term 'substantially' is meant that
the halide, for example, iodide content of the reactant gases (dimethyl ether and
carbon monoxide) and catalyst is less than 500 ppm, preferably less than 100 ppm.
[0035] The primary product of the process is methyl acetate but small amounts of acetic
acid may also be produced. The methyl acetate produced by the process of the present
invention can be removed in the form of a vapour and thereafter condensed to a liquid.
[0036] The methyl acetate may be recovered and sold as such or it may be forwarded to other
chemical processes. Where the methyl acetate is recovered from the carbonylation reaction
products, some or all of it may be hydrolysed to form acetic acid. Alternatively,
the entire carbonylation reaction product may be passed to a hydrolysis stage and
acetic acid separated thereafter. The hydrolysis may be carried out by known techniques
such as reactive distillation in the presence of an acid catalyst.
[0037] The process may be operated as either a continuous or a batch process, preferably
as a continuous process.
[0038] The invention is now illustrated with reference to the following Examples.
Catalyst Preparation
Catalyst A - H-Mordenite
[0039] H-Mordenite (H-MOR) with a silica to alumina ratio of 20 (ex Süd Chemie) was calcined
in a muffle oven (oven-volume = 18L) under a static atmosphere of air. The temperature
was increased from room temperature to 500 °C at a ramp rate of 5°C/min and then held
at this temperature for 24 hours. The mordenite was then compacted at 12 tonnes in
a 33 mm die set using a Specac Press, and then crushed and sieved to a particle size
fraction of 212 to 335 microns.
Catalyst B - Cu-Mordenite - Cu(55)-MOR
[0040] H-Mordenite (40 g) with a silica to alumina ratio of 20 (ex Süd Chemie) was weighed
into a 500 mL round bottomed flask together with 6.43 g of copper (II) nitrate hemipentahydrate
(98% ACS) and a stirrer bar. Sufficient deionised water (ca. 100 mL) was then added
to the flask until a thick slurry was obtained. The top of the flask was then loosely
covered and the flask left to stir overnight. The zeolite was then dried under reduced
vacuum using a rotary evaporator before being dried in an oven at 100 °C for 12 hours.
The zeolite was then calcined in a muffle oven (oven volume = 18L) under a static
atmosphere of air. The temperature was increased from room temperature to 500 °C at
a ramp rate of 5°C/min and then held at this temperature for 24 hours. The zeolite
was then compacted at 12 tonnes in a 33 mm die set using a Specac Press, and then
crushed and sieved to a particle size fraction of 212 to 335 microns. The zeolite
had a Cu loading of 55 mole % relative to A1 contained in the mordenite.
Catalyst C - Ag-Mordenite - Ag(55)-MOR
[0041] This zeolite was prepared in the same way as for Preparation B except that silver
nitrate (99+% ACS) (7.16 g for 50 g mordenite) was used instead of copper (II) nitrate
hemipentahydrate (98% ACS). This resulted in a mordenite having a Ag loading of 55
mole % relative to A1 contained in the mordenite.
Catalyst D -Ag-Mordenite - Ag(70)-MOR
[0042] This zeolite was prepared in the same way as for Preparation B except that silver
nitrate (99+% ACS) (1.82 g for 10g mordenite) was used instead of copper (II) nitrate
hemipentahydrate (98% ACS). This resulted in a mordenite having a Ag loading of 70
mole % relative to A1 contained in the mordenite.
Example 1- Carbonylation of Dimethyl Ether
[0043] Dimethyl ether was carbonylated with carbon monoxide in the presence of zeolite catalysts
A to C, at a range of temperatures 220-350 °C and at a range of pressures 10-50 barg.
The experiments were carried out in a pressure flow reactor unit consisting of 60
identical parallel isothermal co-current tubular reactors of the type described in,
for example,
WO2006107187. The reactors were arranged in 4 blocks of 15 reactors, each block having an independent
temperature control. Into each tube 50, 100 or 200 micro litres of a zeolite catalyst
(designed to give GHSVs corresponding to 4000, 2000 and 1000 h
-1 respectively) is loaded onto a metal sinter having a pore size of 20 micrometers.
All zeolite catalyst samples were heated at a ramp rate of 5 °C/ min. to 100 °C under
98.6 mole % N
2 and 1.4 mole % He at atmospheric pressure at a flow rate of 3.4 ml/ min, and held
at this temperature for 1 hour. The reactor was then pressurised to 10 barg and the
system held at this condition for 1 hour. The gas feed was then changed to a mixture
comprising 63.1 mole % carbon monoxide, 15.8 mole % hydrogen, 19.7 mole % nitrogen
and 1.4 mole % He at a gas flow rate of 3.4 ml/ min, and the system was heated at
a ramp rate 3 °C/ min. to a temperature of 300 °C. The system was then held at this
condition for 3 hours. After this the temperatures of blocks 1 to 4 were adjusted
to 220, 250, 300 and 350 °C respectively, and the system was allowed to stabilise
for 10 minutes. At this point catalyst activation was considered complete, and the
gas feed was changed to a mixture comprising 63.1 mole % carbon monoxide, 15.8 mole
% hydrogen, 14.8 mole % nitrogen, 1.4 mole % He and 4.9 mole % dimethyl ether at a
gas flow rate of 3.4 ml/ min. The reaction was allowed to continue for ca. 78.6 hours
under the above conditions and then the pressure was increased from 10 to 30 barg
and the system was allowed to stabilise for 30 minutes. These conditions were maintained
for ca. 28 hours, and then the pressure was increased from 30 barg to 50 barg. The
system was again allowed to stabilise for 30 minutes and then held at these conditions
for a further 28 hours. The exit stream from the reactor was passed to two gas chromatographs.
One of these was a Varian 4900 micro GC with three columns (Molecular sieve 5A, Porapak®
Q, and CP-Wax-52) each quipped with a thermal conductivity detector. The other was
an Interscience Trace GC with two columns (CP-Sil 5 and CP-Wax 52) each equipped with
a flame ionisation detector. Data was averaged between 50.1 and 78.6 hours to generate
the 10 barg results; between 78.6 and 107.1 hours to generate the 30 barg results
and between 107.1 and 135.6 hours to generate the 50 barg results.
[0044] The productivity and selectivity results of the dimethyl ether carbonylation reactions
are shown in Figs 1 to 6. Productivity, STY
acetyls is defined as the STY for the production of AcOH plus the STY for the production
of MeOAc multiplied by MW
AcOH/ MW
MeOAc. Selectivity was calculated on the basis of ([MeOAc]out + [AcOH]out) / ([DME]in -
[DME]out - 0.5 * [MeOH]out - 0.5 * [MeOAc]out)* 100.
[0045] Fig. 1 depicts productivities achieved at a reaction pressure of 50 barg for each
of the reaction temperatures 220, 250, 300 and 350 °C. Fig. 2 depicts selectivities
to the carbonylation products, methyl acetate and acetic acid, achieved at a reaction
pressure of 50 barg for each of the reaction temperatures 220,250,300 and 350 °C.
Fig. 3 depicts productivities achieved at a reaction pressure of 30 barg for each
of the reaction temperatures 220, 250, 300 and 350 °C. Fig. 4 depicts selectivities
to the carbonylation products, methyl acetate and acetic acid, achieved at a reaction
pressure of 30 barg for each of the reaction temperatures 220, 250, 300 and 350 °C.
Figs 5 and 6 depict productivities and selectivities respectively achieved by operating
at a pressure of 10 barg, 30 barg or 50 barg and at a temperature of 300 °C.
[0046] As can be seen from Figs. 1-4, superior productivities and selectivities are achieved
by operating an anhydrous dimethyl ether carbonylation process at temperatures of
greater than 250 °C and at a pressure greater than 10 barg.
Experiment A - Carbonylation of Methanol
[0047] Methanol was carbonylated with carbon monoxide in the presence of zeolite catalysts
A to D. The experiments were carried out in a pressure flow reactor unit consisting
of 60 identical parallel isothermal co-current tubular reactors of the type described
in, for example,
WO2006107187. The reactors were arranged in 4 blocks of 15 reactors, each block having an independent
temperature control. Into each tube 25, 50 or 100 micro litres of zeolite catalyst
(designed to give GHSVs corresponding to 4000, 2000 and 1000 h
-1 respectively) is loaded onto a metal sinter having a pore size of 20 micrometers.
All catalyst samples were heated at a ramp rate of 5 °C/ min. to 100 °C under 98.8
mole % N
2 and 1.2 mole % He at atmospheric pressure at a flow rate of 3.4 ml/ min, and held
at this temperature for 1 hour. The reactor was then pressurised to the desired pressure
(30 barg, 50 barg or 80 barg) and the system held at the desired pressure for 1 hour.
The gas feed was then changed to a mixture comprising 63.2 mole % carbon monoxide,
15.8 mole % hydrogen, 19.8 mole % nitrogen, and 1.2 mole % He at a gas flow rate of
3.33 ml/ min, and the system was heated at a ramp rate 3 °C/ min. to a temperature
of 300 °C. The system was then held at this condition for 3 hours. After this the
temperatures of blocks 1 to 4 were adjusted to 275, 300, 325 and 350 °C respectively,
and the system was allowed to stabilise for 10 minutes. At this point catalyst activation
was considered complete, and the gas feed was changed to a mixture comprising 63.2
mole % carbon monoxide, 15.8 mole % hydrogen, 9.9 mole % nitrogen and 1.2 mole % He
and 9.9 mol% methanol at a gas flow rate of 3.4 ml/min. Methanol was fed as a liquid
to the inlet of each reactor where it evaporated to give the afore-mentioned gas feed
composition.The reaction was allowed to continue for at least 56.5 hours under the
above conditions The exit stream from the reactor was passed to two gas chromatographs.
One of these was a Varian 4900 micro GC with three columns (Molecular sieve 5A, Porapak®
Q, and CP-Wax-52) each quipped with a thermal conductivity detector. The other was
an Interscience Trace GC with two columns (CP-Sil 5 and CP-Wax 52) each equipped with
a flame ionisation detector. For each of the runs data was averaged over a 28.5 hour
period between ca. 27.8 and 56.3 hours.
[0048] The productivity and selectivity results for carbonylation at 325 °C and at pressures
of 10 barg, 30 barg and 50 barg are given in Figs. 7 and 8. Productivity, STY
acecyls is defined as the STY for the production of AcOH plus the STY for the production
of MeOAc multiplied by MW
AcOH/ MW
MeOAc. Selectivity was calculated as ([MeOAc]out + [AcOH]out) / ([MeOH]in - [MeOH]out -
(2 * [Me20]out) - [MeOAc]out)*100.
[0049] From Figs. 7 and 8, it can be seen the productivities and selectivities for the methanol
carbonylation reactions decrease with increasing pressure. This is in direct contrast
with the productivities and selectivities for the dimethyl ether reactions shown in
Figs. 5 and 6 which increase with increasing pressure.
Example 2 - Carbonylation of Dimethyl ether
[0050] Example 1 was repeated using 25, 50 and 100 microlitres of Catalysts A to D in the
reactors (designed to give GHSV's corresponding to 8000, 4000 and 2000 h
-1 respectively).The reactors were pressurised to 30 barg and the temperature of blocks
1 to 4 was adjusted to 275, 300, 325 and 350 C. The reaction was run with a feed gas
composition of 63.1 mol% carbon monoxide, 15.8 mol% hydrogen, 14.8mol% nitrogen, 1.4
mol% helium and 4.9mol% dimethyl ether at a gas flow rate of 3.4ml/min for 93 hours.
Productivity and selectivity data was averaged over a 27 hour period from 65 to 93
hours. Figs. 9 and 10 depict the productivities and selectivities achieved respectively.
Experiment B - Carbonylation of Methanol
[0051] Experiment A was repeated using a pressure of 30 barg and with a reaftion feed gas
composition of 63.25 mol% carbon monoxide, 15.8 mol% hydrogen, 14.8mol% nitrogen,
1.2 mol% helium and 4.95 mol% methanol at a gas flow rate of 3.4 mol/min. The reaction
was allowed to run for 92 hours. Productivity and selectivity data was averaged over
the period from 65.5 to 92.1 hours. Figs. 9 and 10 depict the productivities and selectivities
achieved respectively.
[0052] Methanol carbonylation in the presence of a zeolite catalyst generally requires a
reaction temperature of greater than 250 °C to achieve acceptable reaction rates.
It has been the view that the carbonylation of dimethyl ether in the presence of a
zeolite catalyst requires the converse, i.e a reaction temperature below 250 °C. However,
Figs. 9 and 10 clearly demonstrate that by operating a zeolite-catalysed carbonylation
of dimethyl ether at both high pressure and high temperature, not only are high productivities
and selectivities achieved but these productivities and selectivities are superior
to those obtained in the carbonylation of methanol employing the same catalysts under
the same reaction conditions.
Example 3
Catalyst Preparation
Catalyst E - H-Ferrierite
[0053] NH
4-Ferrierite with a silica to alumina ratio of 55 (ex Zeolyst) was calcined in a muffle
oven under a static atmosphere of air. The temperature was increased from room temperature
to 110 °C at a ramp rate of 5 °C/ min. and held at this temperature for 2 hours. The
temperature was then increased to 450 °C at a ramp rate of 5 °C/ min and held at this
temperature for 12 hours. The H-ferrierite was then compacted at 12 tonnes in a 33
mm die set using a Specac Press, and then crushed and sieved to a particle size fraction
of 212 to 335 microns.
Catalyst F - Cu-Offretite - Cu(55)-Offretite
[0054] To 0.3 grams of NH
4-Offretite with a silica to alumina ratio of 10 (ex Sintef) was added 430 micro litres
of a solution containing 0.3 grams of copper (II) nitrate hemipentahydrate (98% ACS)
per ml of water. Additional water (to make the total amount of solution added up to
ca. 700 micro litres) was added at the same time and the resultant slurry agitated
on a roller bench for at least 1 hour to ensure thorough mixing. The zeolite was then
dried at 50 °C for at least 16 hours, then at 110 °C for 4 hours before being calcined
in a muffle furnace under a static atmosphere of air. The temperature for calcination
was increased from room temperature to 500 °C at a rate of 2 °C/ min. and then held
at this temperature for 2 hours. The Cu loaded offretite was then compacted at 12
tonnes in a 33 mm die set using a Specac Press, and then crushed and sieved to a particle
size fraction of 212 to 335 microns. The Cu-offretite had a Cu loading of ca. 55 mole
% relative to A1 contained in the offretite.
Carbonylation of Dimethyl Ether
[0055] Example 1 was repeated using 50 micro litres of catalysts E and F in the reactors
(designed to give a GHSV of 4000 hr
-1), at a pressure of 70 barg. After holding the temperature of the reactors at 300
°C for 3 hours the temperature was adjusted to 180 °C and the system allowed to stabilise
for 10 minutes before the gas feed was changed to a mixture comprising 63.1 mol %
carbon monoxide, 15.8 mol % hydrogen, 14.8 mol % nitrogen, 1.4 mol% helium and 4.9
mol % dimethyl ether at a gas flow rate of 3.4 ml/ min. The reaction was allowed to
run under these conditions for 32.2 hours before the temperature was increased to
300 °C. Reaction was then allowed to continue for a further 88 hours. The productivity
results are depicted in Fig. 11.
1. Verfahren zur Erzeugung von Methylacetat, wobei das Verfahren die Carbonylierung eines
Dimethylethereintrages mit Kohlenmonoxid unter im Wesentlichen wasserfreien Bedingungen
derart, dass Wasser in dem Dimethylethereintrag in einer Menge von 2,5 Gew.-% oder
weniger vorliegt, in Gegenwart eines Zeolith-Katalysators, der für die Carbonylierung
wirksam ist, umfasst, wobei die Carbonylierung bei einer Temperatur im Bereich von
mehr als 250 °C bis 350 °C und bei einem Druck im Bereich von 30 bis 80 barg durchgeführt
wird.
2. Verfahren nach Anspruch 1, wobei die Temperatur im Bereich von 275 bis 350 °C liegt.
3. Verfahren nach Anspruch 2, wobei die Temperatur im Bereich von 300 bis 350 °C liegt.
4. Verfahren nach einem der Ansprüche 1 bis 3, wobei die Carbonylierung in Gegenwart
von Wasserstoff durchgeführt wird.
5. Verfahren nach einem der Ansprüche 1 bis 4, wobei der Zeolith mindestens einen Kanal
enthält, der von einem 8-gliedrigen Ring definiert wird.
6. Verfahren nach Anspruch 5, wobei der Zeolith ausgewählt ist aus der Gruppe, bestehend
aus Mordenit, Ferrierit, Offretit und Gmelinit.
7. Verfahren nach Anspruch 6, wobei der Mordenit H-Mordenit oder ionenausgetauscht oder
anderweitig mit mindestens einem Metall, ausgewählt aus der Gruppe, bestehend aus
Kupfer, Nickel, Iridium, Silber, Rhodium, Platin, Palladium und Kobalt, beladen ist.
8. Verfahren nach Anspruch 7, wobei der Mordenit ionenausgetauscht oder anderweitig mit
einem Metall, ausgewählt aus Kupfer, Silber und Gemischen davon, beladen ist.
9. Verfahren nach Anspruch 8, wobei die Metallbeladung im Bereich von 50 bis 120 mol-%,
bezogen auf Aluminium, liegt.
10. Verfahren nach einem der Ansprüche 1 bis 9, wobei zumindest etwas von dem Methylacetatprodulct
zu Essigsäure hydrolysiert wird.
11. Verfahren nach einem der Ansprüche 1 bis 10, wobei der Dimethylether in dem Eintrag
bei einer Konzentration im Bereich von 0,1 mol-% bis 20 mol-%, basierend auf dem Gesamteintrag
(einschließlich rückgeführte Substanzen), vorliegt.
1. Procédé de production d'acétate de méthyle, ledit procédé comprenant la carbonylation
d'une alimentation d'éther diméthylique avec du monoxyde de carbone dans des conditions
essentiellement anhydres telles que de l'eau soit présente dans l'alimentation d'éther
diméthylique en une quantité de 2,5 % en poids ou moins, en présence d'un catalyseur
de zéolithe efficace pour ladite carbonylation, ladite carbonylation étant réalisée
à une température dans la plage allant de plus de 250 °C à 350 °C et à une pression
dans la plage allant de 30 à 80 barg.
2. Procédé selon la revendication 1, dans lequel la température est dans la plage allant
de 275 à 350 °C.
3. Procédé selon la revendication 2, dans lequel la température est dans la plage allant
de 300 à 350 °C.
4. Procédé selon l'une quelconque des revendications 1 à 3, dans lequel la carbonylation
est réalisée en présence d'hydrogène.
5. Procédé selon l'une quelconque des revendications 1 à 4, dans lequel la zéolithe contient
au moins un canal qui est défini par un cycle à 8 éléments.
6. Procédé selon la revendication 5, dans lequel la zéolithe est choisie, dans le groupe
constitué par la mordénite, la ferriérite, l'offrétite et la gmélinite.
7. Procédé selon la revendication 6, dans lequel la mordénite est la H-mordénite ou est
échangée ioniquement ou autrement chargée avec au moins un métal choisi dans le groupe
constitué par le cuivre, le nickel, l'iridium, l'argent, le rhodium, le platine, le
palladium et le cobalt.
8. Procédé selon la revendication 7, dans lequel la mordénite est échangée ioniquement
ou autrement chargée avec un métal choisi parmi le cuivre, l'argent et leurs mélanges.
9. Procédé selon la revendication 8, dans lequel le chargement en métal est dans la plage
allant de 50 à 120 % en moles, par rapport à l'aluminium.
10. Procédé selon l'une quelconque des revendications 1 à 9, dans lequel au moins une
partie du produit acétate de méthyle est hydrolysé en acide acétique.
11. Procédé selon l'une quelconque des revendications 1 à 10, dans lequel l'éther diméthylique
est présent dans l'alimentation à une concentration dans la plage allant de 0,1 %
en moles à 20 % en moles, par rapport à l'alimentation totale (y compris les recyclages).